1. Field of the Invention
The present invention relates to an image processing apparatus and, more particularly, to an image processing apparatus for reading out a video signal from a memory which stores a video signal, and executing processing such as encoding of the readout video signal.
2. Related Background Art
As a conventional apparatus of this type, a movement detection circuit in a digital VTR for converting an image signal into a digital signal, and recording/reproducing the digital signal is known. In this movement detection circuit, after data for one frame are stored in a frame memory, a predetermined number of image data are read out from the memory as one block, a difference between adjacent fields of the readout image data is obtained, and a predetermined calculation is performed using the obtained difference, thereby detecting a movement (interfield correlation) of an image.
However, such a conventional movement detection circuit must have large-capacity memories such as a buffer memory for delay adjustment of interfield correlation calculation, a memory having a capacity corresponding to an image data processing block required upon re-sorting of image data, and the like, and a problem associated with wide distribution of these memories cannot be avoided. In order to divide image data into blocks suitable for frame/field processing before execution of intraframe/intrafield encoding processing, means for re-sorting data, which means includes a memory having a capacity corresponding to an image data processing block, is required, resulting in complicated processing.
Also, the above-mentioned conventional circuit suffers the following drawback since image data is divided into blocks in a frame memory, pixel data in each block are sequentially outputted in the horizontal line direction, and after all pixel data in the horizontal line are outputted, data in the next horizontal line are sequentially outputted.
More specifically, when a difference, in the vertical direction, between adjacent pixel data in a block is calculated, and movement detection is performed on the basis of the total sum of the absolute values of differences, a movement detection unit requires a delay means having at least a delay amount for one horizontal line, and must be designed to have a large delay amount, resulting in a complicated hardware arrangement of the movement detection unit.